pub fn to_multiline_string(lines: Vec<&str>) -> String {
    lines.into_iter().collect::<Vec<&str>>().join("\n")
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn test() {
        let input = vec![
            "1000", "2000", "3000", "", "4000", "", "5000", "6000", "", "7000", "8000", "9000", "",
            "10000",
        ];

        println!("{}", to_multiline_string(input));
    }
}
